Chapter 14 homework

Which of the letters in the figure indicates the vagus nerve?

A The vagus nerve (cranial nerve X) is a component of the parasympathetic cranial outflow. It controls normal function of organs of the thoracic and upper abdominal cavities.

Which pathways compose the autonomic nervous system?

B and C Efferent pathways of the ANS are characterized by a two-neuron chain from the CNS to the effector organ. Both B and C show such an arrangement consisting of both pre- and postganglionic neurons.

assume that the triangular and circular molecules shown in the illustration represent specific neurotransmitters. which of the following best describes the effect on the heart of neurotransmitters released from the postganglionic neurons of B and C?

B would increase heart rate while C would decrease it. Sympathetic stimulation would increase heart rate when under stress, while parasympathetic stimulation would decrease heart rate during "rest and digest." Parasympathetic ganglia are within or near effector organs, while sympathetic ganglia lie nearer to the CNS. Sympathetic postganglionic neurons secrete a different neurotransmitter than somatic and parasympathetic neurons.

Which of the following statements is true of the group of fibers indicated by the letter D?

D indicates fibers that bypass collateral ganglia and terminate within the adrenal gland. Unlike other preganglionic fibers of the sympathetic division, the fibers indicated by D pass through the celiac ganglion to the adrenal gland, where they stimulate the release of norepinephrine into the bloodstream.

The major anatomic difference in autonomic reflex arcs is that there are two sensory afferents.

False The major anatomical difference in autonomic reflex pathways is that there are two motor neurons, the pre- and postganglionic motor neurons.

Unlike the sympathetic division, the parasympathetic division synapses with the adrenal medulla.

False The sympathetic division synapses at the adrenal medulla which enhances the sympathetic responses.

The circular structures shown within pathways B and C represent which of the following?

Ganglia A collection of neuron cell bodies in the PNS is found within ganglion. Note that the ganglia of the sympathetic division are located nearer to the spinal cord, and the ganglia of the parasympathetic division are located nearer to (or within) target organs.

Which of the following is a way in which the somatic and autonomic nervous systems are similar? Which of the following is a way in which the somatic and autonomic nervous systems are similar?

None Each of the factors is different in the somatic and autonomic efferent pathways, respectively.

Which of the following is characteristic of the parasympathetic division?

None of the Above

Which of the following best demonstrates an example of cooperation of the parasympathetic and sympathetic nervous systems?

Parasympathetic stimulation causes vasodilation of blood vessels in the penis, leading to erection; sympathetic stimulation then causes ejaculation. The best example of cooperative autonomic effects is seen in controls of the external genitalia. Parasympathetic stimulation causes vasodilation of blood vessels in the external genitalia, and is responsible for erection of the male penis or female clitoris during sexual excitement. Sympathetic stimulation then causes the ejaculation of semen by the penis or reflex contractions of the vagina during an orgasm.

Once a preganglionic axon reaches a trunk ganglion, one of three things can happen to the axon. Which of the following is NOT one of these three things?

The axon can course back into the spinal cord to synapse with preganglionic neurons in a different spinal segment. Preganglionic axons do not pass back into the spinal cord.

The adrenal medulla secretes epinephrine during sympathetic stimulation. Which of the following statements describes why epinephrine would increase the sympathetic response?

The same receptors that respond to norepinephrine also respond to epinephrine, increasing the action of both. There is no separate receptor for epinephrine. It enhances the sympathetic pathways because it binds to the same receptors as norepinephrine.

The sympathetic division innervates targets with nerves that all originate from the thoracolumbar region.

True The sympathetic division is also called the thoracolumbar division of the autonomic nervous system because the thoracic and upper lumbar spinal segments contain the cell bodies of all preganglionic sympathetic neurons.

Which target organ is not affected by the parasympathetic division of the autonomic nervous system (ANS)?

adrenal medulla The adrenal medulla is not innervated (thus not affected) by the parasympathetic division of the ANS. Preganglionic sympathetic fibers stimulate the adrenal medulla to secrete epinephrine and norepinephrine (hormones that contribute to the overall fight-or-flight response mediated by the sympathetic division of the ANS) into the bloodstream.

Which of the following target organs/systems is affected by the sympathetic nervous system but is NOT affected by the parasympathetic nervous system?

cellular metabolism Preganglionic sympathetic fibers stimulate the adrenal medulla to secrete epinephrine into the bloodstream during "fight-or-flight" situations (such as exercise). In turn, epinephrine increases cellular metabolism (metabolic rate).

Which of the following is not associated with the parasympathetic division of the autonomic nervous system (ANS)?

emergency action The activity of the sympathetic division, often called the "fight-or-flight" system, is evident when we are excited, exercising, or find ourselves in emergency situations.

Which of the following is responsible for the overall integration of the autonomic nervous system (ANS)?

hypothalamus The hypothalamus stands at the top of the control hierarchy as the integrator of ANS activity. The limbic system communicates the hypothalamus, which is why emotions, like fear, affect the ANS. The reticular formation connects the hypothalamus to nuclei in the brainstem that cause the ANS outputs for some visceral organs as their output is regulated by the hypothalamus.

Which plexus does NOT receive innervation from the vagus nerve?

inferior hypogastric plexus The inferior hypogastric plexus receives nerve fibers from the pelvic splanchnic (spinal) nerves, not the vagus (cranial) nerve. As the vagus nerves pass into the thorax, they send branches to the cardiac, pulmonary, and esophageal plexuses. In the abdominal cavity, they send fibers through the large abdominal aortic plexus.

Which description is NOT consistent with the sympathetic division?

most innervation from the vagus nerve The vagus nerve innervates most of the parasympathetic division.

Which receptor pairing below is correct?

nicotinic; acetylcholine Nicotinic receptors are one of two acetylcholine receptors.

Autonomic nerve fibers that increase heart rate, elevate blood pressure, induce dry mouth, and increase sweating do so primarily through the secretion of __________.

norepinephrine Sympathetic fibers primarily release norepinephrine, which can have an excitatory or inhibitory effect.

All somatic motor neurons produce __________.

only acetylcholine Somatic motor neurons activate skeletal muscle fibers at neuromuscular junctions via the neurotransmitter acetylcholine.

Which division of the nervous system has long preganglionic neurons?

parasympathetic The parasympathetic division has long preganglionic fibers and short postganglionic fibers.

Which of these activities is most likely driven by parasympathetic innervation?

resting and digesting The parasympathetic division, sometimes called the "rest and digest" system, keeps body energy use as low as possible, even as it directs vital housekeeping activities like digesting food and eliminating feces and urine.

Which of the following is not an autonomic nervous system (ANS) function?

skeletal muscle reflex The somatic nervous system stimulates skeletal muscle, whereas the ANS innervates cardiac muscle, smooth muscle, and glands.

Which organ receives major input from the sympathetic, but not parasympathetic, division?

skin The smooth muscle of dermal blood vessels and arrector pili are innervated by the sympathetic, but not parasympathetic, division.

Myelination tends to be heaviest on which types of neurons?

somatic motor neurons Somatic motor neurons, those that activate skeletal muscles, are heavily myelinated.

Which of the following is not a designation for sympathetic ganglia?

terminal ganglia Parasympathetic ganglia are also called terminal ganglia because they lie close to or within the target organs.

Which of the following releases the neurotransmitter norepinephrine?

terminus of a sympathetic postganglionic neuron In cases of dual innervation, release of norepinephrine at synapses within effector organs is characteristic of the sympathetic division (B). Sympathetic postganglionic neurons release acetylcholine in areas that receive only sympathetic fibers

The synapse in pathway B has several possible locations. Which of the following is NOT a possible location?

the spinal cord Autonomic synapses are not located within the spinal cord.

Outflow of the sympathetic division occurs from which regions of the CNS?

thoracic and lumbar Preganglionic fibers of the sympathetic division arise from the thoracic and upper lumbar regions (T1 to L2) of the spinal cord.

Which set of details correctly identifies a series of events in a sympathetic pathway?

thoracolumbar origin, short preganglionic fiber, ACh release at ganglion, long postganglionic fiber, NE release at effector

Autonomic motor neurons _________

utilize a two-neuron chain to reach their effectors Autonomic neural pathways utilize two neurons, a preganglionic neuron and a postganglionic neuron, to reach their effector.

Which of the following is an effect of norepinephrine binding to beta 2 adrenergic receptors?

vasodilation The binding of norepinephrine to the beta 2 adrenergic receptors in blood vessels causes vasodilation.

The group of fibers indicated by E represents which of the following?

white rami communicantes The white rami communicantes connect preganglionic fibers from the spinal cord to the sympathetic trunk.

Where are ganglia of the parasympathetic division located?

within or near effector organs Note the location of synapses between preganglionic and ganglionic fibers on the left side of the figure that summarizes the outflow of the parasympathetic division